[time-nuts] 5MHz x 10MHz

Brian, WA1ZMS wa1zms at att.net
Sun Aug 4 22:15:45 EDT 2013


He had no way to quantify the "crud".  There are many
sources of it along the way.

His comments to me were aimed at the amount of contamination that
takes place during the plating of the electrodes on the quartz blank
itself as well as any "crud" that is left from the lapping of the blank.

His main point was that it make take trial and error testing of
say a dozen crystals to find the best of the lot for use in his ULN
oscillators.

My take is that 5MHz is not a fixed & magic number. Just a frequency that
works well for today's frequency standards and can be divided or multiplied
as needed.

As another post on this thread said, there are a number of factors involved
and while 1MHz might be "better", the size of the crystal becomes a
trade-off.

What I don't know fills MANY text books!

-Brian, WA1ZMS

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Hal Murray
Sent: Sunday, August 04, 2013 9:54 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] 5MHz x 10MHz


wa1zms at att.net said:
> In a talking to Charles Wenzel about this very topic some 13 yrs ago, 
> I liked it when he said sometimes it comes down to the "quartz-to-crud
ratio"
> of the crystal that makes all the difference for a given crystal
frequency.

Neat.  Thanks.

How much crud is in a typical modern crystal?

How much was in natural quartz, say from WW II era?

I assume modern crystals are made from quartz grown in a lab using
techniques similar to what the semiconductor industry uses.  Are we talking
ppm or ppb?


Does anybody have any long term stability data on old crystals vs modern
crystals?  Yes, that's not very specific.  By old, I'm remembering the
crystals I saw as a kid (late 1950s).  It was just a few screws to open the
package.  I expect the ARRL handbook had recipes for adjusting the frequency
but my copy from those days is long gone.


--
These are my opinions.  I hate spam.



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